How to get k of an array in php

PHP is a very powerful programming language that is widely used in network application development. In PHP programming, array is a very important data type, which can store large amounts of data and perform fast retrieval.

In some application scenarios, we need to obtain the key values ​​in the array for processing. So, how to get the key value of an array in PHP? This article will introduce and explain this in detail.

1. Use foreach loop to obtain the key value of the array

In PHP, we can traverse the array through the foreach loop and obtain the key value of the array. The following is a simple sample code:

<?php
$array = array("name" => "张三", "age" => 18, "gender" => "男");

foreach($array as $key => $value){
    echo "键：" . $key . "， 值：" . $value . "<br/>";
}
?>

In the above code, we first define an associative array $array, and then use a foreach loop to traverse the array. In the loop body, we can get the key value of the array through the $key and $value variables, which represent the key and value of the array element respectively.

2. Use the array_keys function to get the key name of the array

In addition to using the foreach loop, we can also use the array_keys function provided by PHP to get the key name of the array. The following is a sample code:

<?php
$array = array("name" => "张三", "age" => 18, "gender" => "男");

$keys = array_keys($array);

print_r($keys);
?>

In the above sample code, we first define an associative array $array, then use the array_keys function to get the key name of the array, and save the result in the $keys variable. Finally, we use the print_r function to print out the value of the $keys variable so we can view the results.

3. Use the array_map function to get the key name of the array

In addition, we can also use the array_map function provided by PHP to get the key name of the array. The following is a sample code:

<?php
$array = array("name" => "张三", "age" => 18, "gender" => "男");

$keys = array_map(function($val){
    return $val;
}, array_keys($array));

print_r($keys);
?>

In the above sample code, we use the array_map function to perform a mapping operation on the key name of the array, mapping the original key value to the original value. Since in the above operation, we only returned the original value, the final result is the key name of the array.

4. Use the array_flip function to obtain the key-value swap of the array.

Finally, we can also use the array_flip function provided by PHP to obtain the key-value swap of the array. The following is a sample code:

<?php
$array = array("name" => "张三", "age" => 18, "gender" => "男");

$flipped = array_flip($array);

print_r($flipped);
?>

In the above sample code, we use the array_flip function to perform an operation on the array, swapping the key values ​​​​of the original array, thus obtaining the original value as the key name. A new array with key names and values.

Summary

The above are four ways to get the key value of an array in PHP, including using the foreach loop, array_keys function, array_map function and array_flip function. Different methods are suitable for different scenarios, and we can choose the most appropriate method to operate according to our needs.

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